SAN DIEGO -- Dodgers manager Don Mattingly said he left slumping outfielder Yasiel Puig out of Friday night's lineup because he looked frustrated.

Puig has only two home runs since May 28. In addition, Mattingly said, Puig is 1-for-11 with four strikeouts lifetime against Padres starting pitcher Andrew Cashner.

"It's the right thing to do," said Mattingly, who had Andre Ethier in center field.

But the manager added that Puig, as a high-profile star, needed a chance to "step back and settle down." Mattingly further explained that Puig, as an emotional, high-energy player, needs to "keep himself at a level and consistent place."

Puig struck out pinch-hitting in the seventh inning and is now hitless in his last 19 at-bats.

Mattingly was asked if Puig needs to put in extra work on the field. Puig almost never takes extra batting practice and often is the last player to show up for mandatory pregame work.

"I can't say what he needs," said Mattingly. "I've seen guys here early, I've seen guys in the Hall of Fame that get to the park late, get ready to play, and go. There's not any one way to do it. He has to figure out his way and get ready. He needs the mental approach to keep his body good and his mind right. It's a balance."

Puig tweeted a message to his followers, which translates as: "I thank you to all the fans who continue to rely on me and now I'm going through a bad time but do not worry I'm working to get ready for the last month and the start of the playoffs lets go dodgers #win #baseball # champion #mlb."